The 1361 Shōhei earthquake ( Japanese: 正平地震) was a major earthquake that occurred on August 3, 1361 ( Gregorian calendar) in Japan. [1] It is believed that this quake was one of the Nankai earthquakes. The magnitude was 8.4 Ms ( Richter Scale Magnitude was 8.2 - 8.5 [1]) and it triggered a tsunami. [2] [3]